Occurrence of 222Rn and 226,228Ra in underground water and 222Rn in soil and their mutual correlations for underground water supplies in southern Greater Poland.

European Union Council Directive 2013/51/EURATOM recently sets out so-called indicator parameters for: radon, tritium and indicative dose of water intended for human consumption. The aim of this research was to elaborate an effective procedure for determination of radon and radium 226,228Ra isotopes (which are potentially the main contributors to the internal dose from drinking and cooking water) and to find the possible relationships between these radionuclides in underground water reservoirs and 222Rn concentration in the soil gas in their vicinity. The research was performed by applying a non-volatile and water-immiscible scintillation cocktail based on a pure diisopropylnaphthalene (Ultima Gold F: UGF), which allow for efficient radon extraction from 0.5 dm3 of water samples to 20 cm3 of scintillation phase and its direct determination with a detection limit of 5 × 10-3 Bq dm-3. The further preliminary concentration of 3 dm3 of crude water samples by evaporation to 0.5 dm3 samples led to the removal of all unsupported 222Rn activity and allowed the 226Ra determination via equivalent 222Rn detection after one-month samples storage using a low-background Triathler liquid scintillation counter in the α/ß separation counting mode. Together with determination of 226Ra isotope in water samples, the simultaneous measurements of 228Ra and 222Rn radionuclides concentrations in water as well as 222Rn activity in the soil gas around the water supply sites were performed. The achieved limit of 226Ra detection was at a very low level of 10-3 Bq dm-3. The measured values of 226Ra concentration in 50 public underground water supply units for the Kalisz district of Poland were relatively low and ranged from below detection limit to 28.5 × 10-3 Bq dm-3 with arithmetic mean and median values of 12.9 and 12.2 × 10-3 Bq dm-3, respectively. Weak correlations were observed between activity concentrations of 226Ra and 222Rn in the crude water samples (R2 = 0.31) and 222Rn in water and its concentration in the nearby soil gas (R2 = 0.48).

Distribution of uranium and thorium chains radionuclides in different fractions of phosphogypsum grains.

This work presents results obtained using gamma spectrometry measurements of phosphogypsum samples on a non-fractionated (native) and fractionated phosphogypsum byproduct. The phosphogypsum was divided into particles size fractions within the range of < 0.063, 0.063-0.090, 0.090-0.125, 0.125-0.250, and over 0.250 mm and analyzed after reaching radioactive equilibrium using high-resolution gamma spectrometry technique. It was found that there is no significant differentiation between 226Ra distribution among particular grain size fractions of this material; however, tendency for preferential retention of radionuclides in particular grain size fractions is observed. The detailed analysis of results revealed that radium is preferentially retained in smaller grain size fractions, whereas lead and thorium in coarse fractions. The results indicate that overall 226Ra activity concentrations between particular fractions of phosphogypsum vary globally between - 34 and + 47% regarding non-fractionated material, and for 210Pb activity concentration, fluctuations are found between - 26 up and + 38%. Presumably, the mechanism of radium incorporation into gypsum phase is based on a sequence of radium bearing sulfate phases formation followed by a surface adsorption of these phases on the calcium sulfate crystals, whereas for lead and thorium ions, rather incorporation into crystal lattice should be expected as more likelihood process.

Cesium retention and release from sulfur polymer concrete matrix under normal and accidental conditions.

This paper proposes an efficient two-stage process for stabilization and solidification of the Cs-137 isotope in a sulfur polymer concrete (SPC) matrix. Lignite slag (SL) and fly ash (FA) were applied as active fillers for cesium immobilization. To study the release of Cs-137 isotope and determine the tracer activity in the leachates, we applied a slightly modified ANSI/ANS 16.1 protocol and the gamma spectrometry technique. The measured effective diffusion coefficients for the Cs-137 isotope were between 0.84·10-9 and 3.10·10-9 cm2·s-1. Normalized leaching rates were within the range of 1.74·10-5 - 3.85·10-5 g·cm-2·d-1, fulfilling acceptance criteria for radioactive wasteforms. As well as standard leaching under static conditions, we also studied dynamic leaching of SPC samples at increased temperatures and leaching in an aggressive environment. The Cs-137 effective diffusion coefficients were found to increase by 3 - 4 orders of magnitude (10-6 - 10-5 cm2·s-1), while the normalized leaching rate reached values of up to 2.36·10-3 g·cm-2·d-1 after 28 days of leaching. The proposed cesium immobilization mechanism is based on the formation of cesium silicate and aluminosilicate phases, together with effective matrix sealing during the SPC manufacturing process.

A fast method for the simultaneous determination of soil radon (222Rn) and thoron (220Rn) concentrations by liquid scintillation counting.

This paper presents a fast method dedicated to measurements of radon nuclides in the soil gas. The soil gas is sampled by a typical hollow tube probe by 10 min of sucking of about 3 dm3 of gas and passing it directly through a 16 cm3 of water-immiscible liquid scintillator placed in a typical 20 cm3 scintillation vials, where the radon and thoron nuclides are effectively absorbed. Most of the presently used active methods for radon isotopes determination (e.g., RAD7 or AlphaGuard) require the soil gas transfer to the measuring device. The serious limitation of such approach is the necessity to wait until the radon daughter isotopes decay, before counter is ready for the next measurement. In the proposed method, several samples can be simultaneously gathered from the examined areas in the form of the scintillation vials, which are ready for later measurements in the automatic liquid scintillation counters in the lab or directly in situ. For that purpose, the combined mathematical model for the simultaneous radon and thoron determination has been elaborated. The direct in situ measurements of the sample activity between 60 and 240 s after the end of sampling followed by a second activity measurement after 3 h allow for the determination of both 220Rn and 222Rn concentrations in the soil gas. The limit of detection for 222Rn isotope during 10 min counting is 25 Bq·m-3, whereas for a 3 min counting of 220Rn just after sampling was found to be ca. 150 Bq·m-3. The method was successfully verified and applied for the simultaneous radon and thoron concentrations measurements in the soil gas in Central Poland region.

Numerical analysis and modeling of two-loop experimental setup for measurements of radon diffusion rate through building and insulation materials.

Radon is a natural radioactive gas present in the environment, which is considered as the second most important lung cancer cause worldwide. Currently, radon gas is under focus and was classified as contaminant of emerging concern, which is responsible for serious biological/health effects in human. In presented work we propose the numerical model and analysis method for radon diffusion rate measurements and radon transport parameters determination. The experimental setup for radon diffusion was built in a classical, two chamber configuration, in which the radon source and outlet reservoirs are separated by the sample being tested. The main difference with previously known systems is utilization of only one radon detector, what was achieved by a careful characterization of the Rn-222 source and development of a numerical model, which allows for exact determination of radon transport parameters by fitting simulated radon concentration profile in the outlet reservoir to experimental data. For verification of the developed system, several insulation materials commonly used in building industry and civil engineering, as well as, common building materials (gypsum, hardened cement paste, concrete) were tested for radon diffusion rate through these barriers. The results of radon transmittance, permeability and diffusion coefficients for investigated materials are in compliance with values known previously from the literature. The analysis method is fast and efficient, and requires measurement period varying from a dozen or so hours up to 2-3 days depending on material properties. The described method is entirely based on a numerical analysis of the proposed differential equation model using freely available SCILAB software and experimental data obtained during sample measurements.

Influence of electron beam irradiation on water-saturated biodiesel.

The objective was to study changes in water-saturated biodiesel irradiated by electron beam and to analyse them considering the influence of absorbed dose. Based on obtained results it can be concluded that irradiation did not affect ester groups in FAME molecules, but strongly influenced on double bonds. Total ester content decreased linearly with the increase in absorbed dose, causing FAME not to meet the requirement of PN-EN 14214 concerning the ester content (96.5 wt%). Therefore, the use of ionizing radiation to improve biodiesel properties is unlikely, but it is worth to consider electron beam sterilisation of this biofuel.

Optimization of the heavy metal (Bi-W-Gd-Sb) concentrations in the elastomeric shields for computer tomography (CT).

Eight elastomeric composites (NRU, GR1-GR4, NRBG08-NRBG24) containing mixtures of different proportions of heavy metal additives (Bi, W, Gd and Sb) have been synthesized and examined as protective shields. The NRU sample was a pure rubber matrix and served as a reference sample for heavy metal modified composites. Experimental procedure used for evaluation of the composite shields and their attenuation properties was based on the utilization of HPGe spectrometry and analysis of X-ray fluorescence radiation intensity of the heavy metal additives in the following energy ranges for: Sb (20-35 keV), Gd (35-55 keV), W (55-70 keV) and Bi (70-90 keV). The main contributor to the induced X-ray fluorescence radiation within the shield is Bi additive and the intensity of the X-ray radiation generated within the energy range of 70-90 keV strongly depends on its concentration. It was found that decreasing concentration of the Bi fraction from 0.35 (GR samples) to 0.15 (NRBG samples) results in significant lowering Bi X-ray fluorescence radiation within the 70-90 keV energy range. Secondary effect of decreasing Bi concentration was efficient diminishing excitation processes for lower Z heavy metal additives (W, Gd and Sb, GR vs. NRBG samples). As the final quality parameter of the shielding properties for the examined elastomers, dose reduction factor (DRF) coefficients were calculated for each shield. It was found, that the best shielding properties are observed for composites with lower Bi concentration (0.15 vs. 0.35 Bi mass fraction) with only slight further improvement of their parameters (DRF) with increasing of Gd concentration (Gd mass fraction 0.08, 0.16 and 0.24). The most efficient dose reduction composite was found to be NRBG24 elastomer with DRF value 0.47 (53 % dose reduction) for ca. 2 mm and 0.44 g/cm2 layer thickness.

Cytotoxic activity of the selected pyridinium salts against murine leukemia L1210.

The objective of this work was to evaluate the relationship between chemical reactivity of 3-substituted pyridinium salts and their cytotoxic properties against murine leukemia L1210. Chemical reactivity of pyridinium salts towards NADH oxidation following one-step hydride transfer depends strongly on their redox properties. The investigated reaction may reflect the ability of the salts to deplete NADH level in cells and to affect their metabolic functions. On the other hand, the cytotoxic activity against murine leukemia cells, expressed as ED50 values, varied strongly depending upon the compound used. The investigated salts showed also a diverse antileukemic effect in in vivo experiments as measured by the increase in the survival time of L1210 leukemia-bearing mice. These biological effects were correlated with equilibrium constants found for the reaction of pyridinium salts with NADH.

Radical scavenging and NO-releasing properties of selected beta-adrenoreceptor antagonists.

It is claimed that novel beta-adrenolytic drugs possess superior antioxidant properties as compared to classical selective or non-selective beta-adrenoceptor antagonists. Here we tested this notion by analyzing radical scavenging properties of selected beta-adrenolytic drugs and their ability to release nitric oxide in biological preparations. Selective beta1-adrenolytics such as nebivolol, atenolol, metoprolol and non-selective beta-adrenolytics with alpha1-receptor blocking properties such as carvedilol and labetalol were chosen for analysis. NO-releasing properties of nebivolol and carvedilol distinguished third generation beta-adrenolytics from their older counterparts while the reactivity towards hydroxyl and peroxyl radicals discerns only carvedilol but not nebivolol. Thus, superior clinical efficacy of third generation beta-adrenolytics may be related to their ability to release NO rather then to their direct antioxidant properties.

Anthralin: primary products of its redox reactions.

One-electron reduction significantly enhances the ability of anthralin, 1, to act as a hydrogen atom donor. On annealing of an MTHF glass in which the radical anion of anthralin, 1*-, is generated radiolytically, this species decays mainly by loss of H* to give the anthralyl anion, 2- . On the other hand, radicals formed on radiolysis of matrices that are suitable for the generation of radical anions or cations are capable to abstract H* from anthralin to give the anthralyl radical, 2* . Both 2- and 2* are obtained simultaneously by mesolytic cleavage of the radical anion of the anthralin dimer. Contrary to general assumptions, the anthralyl radical is found to be much more reactive toward oxygen than the anion. All intermediates are characterized spectroscopically and by reference to quantum chemical calculations. Attempts to generate the radical cation of anthralin by X-irradiation of an Ar matrix containing anthralin led also to significant formation of its radical anion, i.e., anthralin acts apparently as an efficient electron trap in such experiments.

Mechanistic aspects of alloxan diabetogenic activity: a key role of keto-enol inversion of dialuric acid on ionization.

The inversion of the keto-enol stability order of dialuric acid on ionization was calculated and verified experimentally. The radical cations in both forms were characterized. The spectrum of the keto form was observed upon direct ionization of dialuric acid under matrix conditions, whereas the enol form was formed upon a sequential electron-proton-proton attachment to alloxan under acidic aqueous condition. Facilitation of the one-electron oxidation of dialuric acid upon its enolization can result in a more effective formation of superoxide radical anion in the process of its auto-oxidation. This process is discussed in reference to the alloxan diabetogenic action. Both neutral keto and enol forms are energetically close, and under favorable conditions, the auto-oxidation of dialuric acid could involve participation of the enol form.